linux-kernel - Re: [PATCH v1 08/16] arm64: dts: mt8195: Add power domains controller

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <0301ebc6-1222-e813-f237-f14ad8444940@linaro.org>
Date:   Wed, 6 Jul 2022 17:18:40 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Tinghan Shen <tinghan.shen@...iatek.com>,
        Yong Wu <yong.wu@...iatek.com>, Joerg Roedel <joro@...tes.org>,
        Will Deacon <will@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Chun-Jie Chen <chun-jie.chen@...iatek.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Weiyi Lu <weiyi.lu@...iatek.com>
Cc:     iommu@...ts.linux-foundation.org,
        linux-mediatek@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Project_Global_Chrome_Upstream_Group@...iatek.com
Subject: Re: [PATCH v1 08/16] arm64: dts: mt8195: Add power domains controller

On 06/07/2022 14:00, Tinghan Shen wrote:
> Hi Krzysztof,
> 
> After discussing your message with our power team, 
> we realized that we need your help to ensure we fully understand you.
> 
> On Mon, 2022-07-04 at 14:38 +0200, Krzysztof Kozlowski wrote:
>> On 04/07/2022 12:00, Tinghan Shen wrote:
>>> Add power domains controller node for mt8195.
>>>
>>> Signed-off-by: Weiyi Lu <weiyi.lu@...iatek.com>
>>> Signed-off-by: Tinghan Shen <tinghan.shen@...iatek.com>
>>> ---
>>>  arch/arm64/boot/dts/mediatek/mt8195.dtsi | 327 +++++++++++++++++++++++
>>>  1 file changed, 327 insertions(+)
>>>
>>> diff --git a/arch/arm64/boot/dts/mediatek/mt8195.dtsi b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
>>> index 8d59a7da3271..d52e140d9271 100644
>>> --- a/arch/arm64/boot/dts/mediatek/mt8195.dtsi
>>> +++ b/arch/arm64/boot/dts/mediatek/mt8195.dtsi
>>> @@ -10,6 +10,7 @@
>>>  #include <dt-bindings/interrupt-controller/irq.h>
>>>  #include <dt-bindings/phy/phy.h>
>>>  #include <dt-bindings/pinctrl/mt8195-pinfunc.h>
>>> +#include <dt-bindings/power/mt8195-power.h>
>>>  
>>>  / {
>>>  	compatible = "mediatek,mt8195";
>>> @@ -338,6 +339,332 @@
>>>  			#interrupt-cells = <2>;
>>>  		};
>>>  
>>> +		scpsys: syscon@...06000 {
>>> +			compatible = "syscon", "simple-mfd";
>>
>> These compatibles cannot be alone.
> 
> the scpsys sub node has the compatible of the power domain driver.
> do you suggest that the compatible in the sub node should move to here?

Not necessarily, depends. You have here device node representing system
registers. They need they own compatibles, just like everywhere in the
kernel (except the broken cases...).

Whether this should be compatible of power-domain driver, it depends
what this device node is. I don't know, I don't have your datasheets or
your architecture diagrams...

> 
>>> +			reg = <0 0x10006000 0 0x1000>;
>>> +			#power-domain-cells = <1>;
>>
>> If it is simple MFD, then probably it is not a power domain provider.
>> Decide.
> 
> this MFD device is the power controller on mt8195. 

Then it is not a simple MFD but a power controller. Do not use
"simple-mfd" compatible.

> Some features need 
> to do some operations on registers in this node. We think that implement 
> the operation of these registers as the MFD device can provide flexibility 
> for future use. We want to clarify if you're saying that an MFD device 
> cannot be a power domain provider.

MFD device is Linuxism, so it has nothing to do here. I am talking only
about simple-mfd. simple-mfd is a simple device only instantiating
children and not providing anything to anyone. Neither to children. This
 the most important part. The children do not depend on anything from
simple-mfd device. For example simple-mfd device can be shut down
(gated) and children should still operate. Being a power domain
controller, contradicts this usually.

Best regards,
Krzysztof